Rising damp and dry rot survey, of West Ashton Church in Wiltshire

Complete Preservation received an instruction from a previous client who is a member of St John’s Church West Ashton Wiltshire, to find out why the walls are suffering from damp issues and the timber floor is suffering from dry rot.

The Vestry of the Church was one of the issues that needed to be investigated first of all, this had a suspended timber floor covered with a carpet. The walls were plastered with a lime plaster, not exactly the original as pictures revealed earlier there was a stone finish. Some later repairs to the lime plaster had been carried out with a lime renovating plaster.

Visual damp issues were evident to the walls, along with peeling paint and blistering plaster, all indicative of a long term issue. We undertook a full vertical profile, following the methodology in BRE Digest 245. Taking these plaster samples allows us to see how much moisture is in the wall, and if there are hygroscopic salts present and if so the distribution and the amount.This helps us differentiate between rising damp issues caused by possibly mains water leaks / defective soak aways etc.

Interestingly what caused a difference in opinion between previous surveyors is that a slate damp proof course was present in the walls-visible externally. It is very rare for a slate damp proof course to fail, i’ve personally never seen one.

When I inspected the sub floor, it was very clear there was a wet rot issue, this was definitely not a dry rot issue as per instruction (they were very happy). The floor had a very shallow void and there was virtually no sub floor ventilation, some timbers had debris pushed up against them, its no wonder they were decayed.

Beneath the floor there is the old boiler room, this has a vaulted ceiling, and this ceiling is actually bridging the slate damp proof course-which is the cause of the rising damp problem…..problem solved, sort of!

After taking the plaster samples it takes us around 7 days for the analysis to be finished to get the results. It revealed severe rising damp, this being the free moisture at the base of the wall was 22%.

There were other factors relating to atmospheric moisture problems in the Church, which to be fair is typical as there normally very cold and then quickly heated whilst occupied. We carried out some data logging of the floor void to see what was going on under there just to really see how bad things were. As you can see the floor is at dew point, the relative humidity goes to over 100%….please ignore this, as the data loggers go wild when they get to this rh.

Below is graphs showing the distribution of rising dampness and hygroscopic salts. The first graph shows just the hygroscopic and the capillary. Notice the salt band at around 1250mm.

The below graph is the same graph, just with total moisture content. I find sometimes this can be confusing for people and the above is easier to understand.

The repair

The thick stone walls can’t have a damp proof course injected as it would be highly unlikely to work, the lime plaster has failed previously, and also some of the more recent modern lime renovating plaster. So we know from the data collected and the survey, we can’t dry this wall down, and it has a significant rising damp issue. It is very unlikely that the lime plaster would last as the previously applied ones have failed.

It was decided by the Architect and the The Diocesan Advisory Committee to use a ventilated timber panelling system to isolate the damp wall, along with a new oak floor.

Complete Preservation carried out the survey along with the sympathetic remedial works to the Church. It was a pleasure for us to work on this beautiful Listed Building!

The review

The job in hand was to replace the small vestry wooden floor (2400mm x 2400mm) which had become unsafe; install under floor vents; install new wooden timber floor and remove plaster from walls and apply wooden cladding. Complete Preservation visited the site and provided a very comprehensive and in-depth quotation. Various moisture and damp testing was undertaken and monitoring of atmospheric changes recorded. Once the work had commenced and the old floor had been removed, it revealed rotten joists. These had to be replaced. Great patience was given when liaising with client and architect. Complete Preservation worked very sympathetically with the Grade II building and made every attempt to keep noise and dust to a minimum; plus keeping the client informed of all works being addressed and an explanation why this work was being undertaken; plus giving timescales of proposed work. Although the job proved more troublesome than initially envisaged, all criteria and specifications were met and the finished vestry was a credit to the company and to the men who worked on the task of refurbishing the room. The team worked diligently; worked in an orderly and tidy fashion; took care of their surroundings and took pride in their work. I would not hesitate to recommend Complete Preservation’s services or if the need arose, to engage them on any future work.

I spoke to a local Chartered surveyor who gave me your details and thinks you would be more suited to survey my issues. How much does this type of survey cost please? I have lots of damp problems in my property, some of which I think are rising damp, or these hygroscopic salts I’ve been reading about. Thanks Steph